Many hand held digital devices, such as smart phones (e.g., iPhone), tablet computers (e.g., iPad) and digital cameras, are operated by touch screen input devices. A touch screen is normally a display screen which can identify the occurrence and position of a touch within a display region. The word “touch” usually refers to touch by a finger or body part of a user. It interacts with what is displayed on the screen rather than other input device, such as a keyboard, a mouse or a touch pad which interacts in an indirect way. There are many different types of touch screen available today. The most common types being used by hand held devices, such as smart phones, tablet computers and digital cameras are resistive and capacitive touch screens.
A resistive touch screen includes a glass sheet coated with a thin conductive layer and a metallic layer. The two layers are separated by a spacer. When a user makes contact with the touch screen, the two layers touch each other at the same location. The change in electric current will be identified and computed to a set of coordinates on the touch screen display. A resistive touch screen can be operated by fingers or by many types of object as long as it can provide pin point compression on the touch screen.
Another type of touch screen is capacitive touch screen. A capacitive touch screen includes a thin conductive layer such as Indium Tin Oxide, which is visually transparent. It stores electric charge and is positioned on a glass layer of the display. When a user makes contact with the touch screen, usually with a bare finger, small quantity of electric charge is transmitted to or from the user's finger. The quantity of electric charge on the touch screen at the designated position is reduced or increased. This change in electric charge is detected and computed to a set of coordinates on the display. A finger usually works well with capacitive touch screen. A human body is a good transferor and transferee of electric charge because of the electromagnetic field around the human body at all times. A device composed of compatible materials with good conductivity of electric charge can perform the function. However, a pencil or stylus which is workable on a resistive touch screen is not workable on a capacitive touch screen.
As previously mentioned, these touch screens can be used in many hand held digital devices. These digital devices may not be waterproof, and therefore cannot be used in wet or underwater environment. If a user wants to operate those devices in such environment, a waterproof case or housing would have to be used to encapsulate those digital devices in order to avoid water going into the digital devices and damaging the electronics, mechanical or optical components inside. These kinds of waterproof case can either be soft or hard. It usually has an opening allowing the user to load the digital device into the waterproof case. It usually has a locking mechanism for locking and sealing the waterproof case.
For soft waterproof cases, a user can control some of the features of the digital devices such as push buttons, rocker switches or levers from outside of the soft case by fingers. This type of soft case can also be used for devices with resistive touch screens. Some soft cases are compatible with devices having capacitive touch screens. This type of soft case can transfer electric charge to and fro between the human body and the capacitive touch screen in certain environment and conditions. In some situation, the inner surface of the soft waterproof case is in close contact with the capacitive touch screen due to, for example, insufficient air inside the case or the air inside the case is being compressed by water pressure when the waterproof case containing the digital device is immersed in water to a certain water depth.
Besides soft waterproof cases, there are hard waterproof housings for handheld digital devices. A hard waterproof housing can provide better protection to the digital devices against impact and it can go much deeper in water than soft waterproof cases because it can withstand water pressure to a certain depth without compressing the air inside the waterproof case. Due to its “hard” property, access from outside of the housing to the digital device inside the housing with a user's finger or body part without any mechanism is impossible.
Therefore, there is a need to provide a specially designed actuator mechanism for actuating a capacitive touch screen of a digital device inside a waterproof housing.
The above description of the background is provided to aid in understanding a waterproof housing and its actuator mechanism, but is not admitted to describe or constitute pertinent prior art to the waterproof housing and its actuator mechanism disclosed in the present application, or consider any cited documents as material to the patentability of the claims of the present application.